The Astrophysics of the PLATO Space Mission-‐ “Living with Stars”
The astrophysics of the PLATO space mission-
“Living with Stars” Cosmic Vision is centered around four Grand Themes: 1. What are the conditions for planet formation and the emergence of life? • From gas and dust to stars and planets • From exo-planets to biomarkers • Life and habitability in the Solar System 2. How does the Solar system work? 3. What are the Fundamental Physical Laws of the Universe? 4. How did the Universe originate and what is it made of? Cosmic Vision is centered around four Grand Themes: 1. What are the conditions for planet formation and the emergence of life? • From gas and dust to stars and planets • From exo-planets to biomarkers • Life and habitability in the Solar System 2. How does the Solar system work? 3. What are the Fundamental Physical Laws of the Universe? 4. How did the Universe originate and what is it made of?
First: In-depth analysis of terrestrial planets. Next: Understanding the condi ons for star & planet forma on, and the origin of life. Later: Census of Earth-sized planets, explora on of Jupiter’s moon Europa. Finally: Image terrestrial exoplanet. The PLATO mission statement From planet frequency to planet characterization
PLATO 2.0 addresses the ESA Cosmic Vision science questions: What are the conditions for planet formation and the emergence of life? How does the Solar System work?
PLATO 2.0 follows the recommendations of ESA’s Exoplanet Roadmap Advisory Team (EPRAT 2008 – 2010) The PLATO mission statement From planet frequency to planet characterization
PLATO shall, using the transit method & asteroseismology, discover and characterise large numbers of small, close by planets. (ESA‘s EPRAT roadmap 2010) • Precision in exoplanet radius < 2% and mass < 10% • Precision in age is < 10 – 20 % The result will be a catalogue with : • The planetary Masses, Radii Mean density as well as constraining the scale height and composition of the atmosphere • The Age puts the planets into an evolutionary sequence • The catalogue provides the necessary unique data allowing future spectroscopic studies and interpretation of exo-atmospheres, potential biospheres and ultimately searching for biomarkers Ultimate goal of exoplanetology is to understand ourselves!
Where we come from?
Where we are going?
Where and when does life arise? How does it evolve?
Is the Earth unique, has life developed elsewhere?
What makes a planet habitable? Fundamental questions:
Did the Earth form in a special place in the Universe and/or under extraordinary circumstances?
How diverse are planets and planetary systems?
What are the characteristics of terrestrial planets in the habitable zones of stars?
How do planetary systems form and evolve?
Is our Solar system special? Place the Solar System in context!
Carry out Comparative Planetology across interstellar distances viz.
- Analyse Solar System objects through observations and in-situ measurements!
- Define parameters measurable across interstellar distance to compare systems!
- Observe large enough sample to be statistically significant and to study evolution! Understanding the star – planet connection!!! “Living with a star”
- How do the formation process impact both star and planet(s)?
- How do the stellar evolution impact the planetary evolution – and vice versa?
- How does the star and stellar evolution impact the habitability – and life itself ? To answer these questions, we need to find planets of all kinds but particularly small Earth-like ones
We need to determine physical parameters with high precision -
first Mp, Rp, ages We need to do this for a large sample
We are going to use two of the most common methods
ones to give you (Mp, Rp, and with a new twist, The ages)
3 Where do the error bars come from? M p sini P 3/2 ( ) = K 3 1− e2 2 2πG ( ) (M* + M p )
2 F − F $ R ' ΔF = no−transit transit = & P ) Fno−transit % R* (
So if we need to know the planetary mass, radii, with a precision € better than ~ few % we must know the parameters of the star to the same precision Planet diversity from CoRoT, Kepler and MOST
The need for bright stars
• Lessons learned from CoRoT and Kepler: Future transit missions must target bright stars • TESS (NASA): Scans the ~ whole sky, 1 month per field. 2% of sky will be covered during several hundred days, 4 x10cm telescopes offset • CHEOPS (ESA/CH+partners) Follow-up of RV • K-2 Kepler extension 80 d/field along eclip c The need for bright stars The need for bright stars
PLATO 2.0 will detect and bulk characterise small planets in the HZ of solar-like stars
The PLATO 2.0 Mission Selected as ESA‘s M3
• PLATO will provide a large catalogue of highly accurate bulk planet parameters: • radii (transit) • masses (RV follow-up) • mean densities • ages (astroseismology) • well-known host stars
• Focus on warm/cool Earth to super-Earths, up to the habitable zone of solar-like stars
• Focus on solar-like host stars to put the Solar System into context
• Observe bright stars for feasible RV follow-up and targets for atmosphere spectroscopy by e.g. JWST, E-ELT, future space missions
• Provide a huge legacy for planetary, stellar and galactic sciences
The Method(in summary)
Characterize bulk planet parameters Accuracy for Earth-like planets around solar-like (F – K) MS stars: Techniques Example: Kepler-10 b . Radius < 2% Photometric transit . mass < 10% . age known to ~ 10%
bright host stars: RV – follow-up
Asteroseismology range
PLATO prime PLATO detection
Understand the stars themselves around which the planets orbit
Spectroscopy has so far been the most important tool PLATO 2.0 will have to provide stellar physics in bulk!! To determine the mass, the radius and the age of the star with high accuracy
Here P-modes are the key
Asteroseismology – providing mass and age of host stars
3 1. Large separa ons Δ0 ∝ √M/R mean density
2. Small separa ons d02 probe the core age 3. Inversions + mode fi ng consistent ρ, M, age Asteroseismology has been successfully applied to bright Kepler stars, showing how powerful this technique is. Kepler asteroseismology
P-modes in Hat-P-7
Blow-up showing l=0,1,2
Δν0 for l = 0,1,2; filled symbols is data, open is model 3 Kepler asteroseismology
Kepler result is following:
Planet parameters are now known to < 5% instead of >50%!!! 2010ApJ...713L.164C Christensen-Dalsgaard et al
So is there any way around having to do asteroseismology for every host star?
NO!!
If we want to be able to determine other physical aspects like atmospheric composition, stratification, evolutionary stage, etc Asteroseismology Not even Darwin or TPF can avoid needing this information PLATO instrument Very wide field + large collecting area : multi-instrument approach
Two designs that can do the job
• Cameras are in groups • Offset to increase FoV • Nominal mission covers ½ the sky
Multi-telescope approach give - Large FOV (Large number of bright stars) - Large total collecting area (provides high sensitivity allowing asteroseismology) - 32 « normal » 12cm cameras, cadence 25 sec - 2 « fast » 12cm cameras : cadence 2.5 sec, 2 colours
- dynamical range: 4 ≤ mV ≤ 16 - Nominal mission 6 years, FOV 48.5 x 48.5 deg = 2250 sq deg 34 Basic observation strategy very wide field + 2 successive long monitoring phases: 3 years + 2 years comply with dura on requirement
Kepler 120° PLATO 150° 90°
180°
60°
CoRoT CoRoT 210° 22h 20h 18h 16h 14h 12h 10h 8h 6h 4h 2h 0h 30°
240°
0°
270° 330°
300° PLATO
ESA Cosmic Vision Dec 1 2009 PLATO: PLAnetary Transits and Oscillations of stars 35 Basic observation strategy step and stare phase (1 year) : N fields for 3-5 months each - increase sky coverage - poten al to re-visit interes ng targets - explore various stellar environments
25% of the whole sky ! Kepler 120°
PLATO 150° 90°
180°
60°
CoRoT CoRoT
210° 22h 20h 18h 16h 14h 12h 10h 8h 6h 4h 2h 0h 30°
240°
0°
270° 330°
300° PLATO
ESA Cosmic Vision Dec 1 2009 PLATO: PLAnetary Transits and Oscillations of stars 36 Basic observation strategy step and stare phase (2 years) : N fields for 3-5 months each - increase sky coverage - poten al to re-visit interes ng targets - explore various stellar environments 42% of the whole sky ! Kepler 120°
150° 90° PLATO
180°
60°
CoRoT CoRoT
210° 22h 20h 18h 16h 14h 12h 10h 8h 6h 4h 2h 0h 30°
240°
0°
270° 330°
300° PLATO
ESA Cosmic Vision Dec 1 2009 PLATO: PLAnetary Transits and Oscillations of stars 37 Number of light curves Follow-up PLATO is not the end....
It is not even the beginning of the end....
But maybe, just maybe, it is the end of the beginning....
Winston S Churchill